In connection with microscopes, in particular, users need to know the distance from their object to the objective of the microscope.
The most varied methods have been proposed for this purpose. For example, there are transit-time measurements using pulse-coded laser beams. Various optical methods, such as the split-image method or triangulation method, are also known. Thus, for example, the so-called MKM microscope design from the Zeiss company applies a pulsing laser beam which is directed onto the focus. If the object plane is located in the Z-direction upstream or downstream of the focal plane, the laser luminous point blinks left or right of the optical axis of the microscope. Whereas the first method is electronically complicated and affected by functional errors, the second method requires a substantial optical outlay.